Can Antioxidants Really Improve Your Athletic Performance?

A senior sports scientist explains why an antioxidant overload could actually hinder your athletic abilities

As an athlete, whether recreational or elite, you’re always looking for any extra edge that can improve your performance. Health and fitness is a priority for you and you work hard to reach your goals, so you’re interested in anything that can provide an extra advantage.

I’m willing to bet that you’ve heard about how antioxidants are good for your health, and you may even use antioxidant infused energy supplements that claim to help improve your athletic performance.

Those claims aren’t necessarily false, and antioxidants are definitely good for your health. But there’s more to the story than what product labels with buzzwords are revealing.

“There is little evidence to suggest improved performance gains when habitually taking antioxidants," says Katie M. Slattery, Ph.D, a Senior Sports Scientist in exercise physiology at the New South Wales Institute of Sport in Australia. “My personal opinion is that antioxidant supplementation should be periodised, just like any training program.”

Slattery explained that antioxidants are substances that help minimize oxidative damage.

“Oxidants or ‘free radicals’ have an unpaired electron, which makes them highly reactive with other molecules. Left uncontrolled, oxidants can cause a cascade of reactions which damage the cellular structure of lipids, protein and DNA,” she said.

Antioxidants are important because they counteract oxidants by giving them an electron which stabilizes the reactive molecule.

According to Slattery some of the most well-known dietary sources of antioxidants include vitamin C and E, but past studies have found that these do very little to enhance athletic performance.

“Researchers have since begun to focus on other antioxidant substances such as N-acetylcysteine and polyphenols, finding more promising results,” she said. “Our recent study demonstrated a significant improvement in repeat sprint capacity in cyclists following a nine-day supplementation with N-acetylcysteine.”

She also made note of two other studies, one that revealed improvements in a 30km cycling time trial with twice daily consumption of a formula containing the antioxidant quercetin (MacRae et al., 2006), and another that demonstrated improved power output during resistance training after ingestion of a drink high in polyphenols (Ackerman et al., 2014).

“However, it should be noted that these performance gains have not been consistently shown in all investigations,” she said.

In other words, there are likely performance benefits associated with the intake of certain antioxidants, but more research is needed to know for sure.

Slattery most recommends antioxidant supplementation for athletes who frequently train at high intensities and over prolonged periods of time.

“During exercise there is an increase in oxidant production. In small amounts, these oxidants are beneficial to performance and help the body to adapt to exercise. However, in large amounts, oxidants can interfere with muscle contraction and a sustained elevation can lead to a state of chronic inflammation and a reduced capacity to fight infections,” she said. “When exercise is prolonged or performed at high intensities, antioxidant supplementation can have an ergogenic effect by maintaining the optimal amount of oxidant production to maintain muscular contraction.”

And the reason that she recommends supplementing with antioxidants periodically: some studies have revealed that an antioxidant overload could potentially hinder performance.

“Oxidants also play an important role in signalling the body to adapt to exercise,” she said. “Excessive antioxidant intake may reduce the ability of oxidants to send these messages which in turn may blunt the adaptive processes to exercise.”

Some research suggests that too much antioxidant supplementation could diminish the positive effects of exercise at a cellular level (Paulsen et al. 2014), but again Slattery notes that further research is needed to know for sure, especially to determine whether or not the effect translates to a long term decline in performance.

The bottom line: Slattery first and foremost recommends obtaining antioxidants naturally through a nutrient-dense, whole foods diet.

“Considering the potential negative effects of long term supplementation, it makes sense to ensure adequate antioxidant intake through dietary sources rather than rely on supplements,” she said. “Then use antioxidant supplementation during competition or to provide additional support if required during heavy training blocks or at the onset of illness.”

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Slattery KMDascombe BWallace LKBentley DJCoutts AJ (2014) “Effect of N-acetylcysteine on cycling performance after intensified training.” Med Sci Sports Exerc. Jun;46(6):1114-23. doi: 10.1249/MSS.0000000000000222.

Ackerman JClifford TMcNaughton LRBentley DJ1 (2014) “The effect of an acute antioxidant supplementation compared with placebo on performance and hormonal response during a high volume resistance training session.” J Int Soc Sports Nutr. Mar 21;11(1):10. doi: 10.1186/1550-2783-11-10.

MacRae, H. S. and K. M. Mefferd (2006). "Dietary antioxidant supplementation combined with quercetin improves cycling time trial performance." International Journal of Sport Nutrition and Exercise Metabolism 16(4): 405-419.

Paulsen G1, Cumming KTHolden GHallén JRønnestad BRSveen OSkaug APaur IBastani NEØstgaard HNBuer CMidttun MFreuchen FWiig H,Ulseth ETGarthe IBlomhoff RBenestad HBRaastad T. (2014) “Vitamin C and E supplementation hampers cellular adaptation to endurance training in humans: a double-blind, randomised, controlled trial.”